For designing a voltage converter with protection against reversed polarity, it is known to have a diode full bridge rectifier between the input side connectors and the actual voltage converter. This circuit design causes conduction losses within the diodes. Additionally, the input voltage between the input side connectors needs to be distinctly above twice the bias voltage of the diodes. The reference between the potentials at the input side connectors and the output side connectors of such a voltage converter is undefined; and a power flow may happen unidirectionally only from the input side connectors to the output side connectors.
The known circuitry described above may also be used for forming a power factor optimized AC/DC converter by using the input side connectors not for a DC input voltage of unknown polarity but for an AC input voltage. The disadvantages mentioned above for the known circuitry also occur with this application.
Further, a so-called “Bridgeless Power Factor Correction” stage, also called a “Bridgeless PFC” stage is known for designing a power factor optimized AC/DC converter. Therein a combined diode/transistor full bridge is provided, whereto the input side AC voltage is connected via one or more inductors. In addition to the disadvantages mentioned for the AC/DC converter as described above, this circuitry exhibits the further disadvantage that the DC output voltage between the output side connectors may not get lower than the peak value of the input side AC voltage, as long as no additional DC/DC converter is provided.
A four quadrant chopper (4 QC) in the form of a full bridge made of switches with parallel diodes, in which each of the half bridges is connected to one of the output side connectors via an inductor and which is, for example, known for controlling a DC motor, has the disadvantages that the output voltage can never exceed the input voltage without a further DC/DC converter, and that the reference between the potentials at the input side connectors and the output side connectors is not defined.
The disadvantage of the undefined reference between the potentials at the input side connectors and the output side connectors is overcome by a four quadrant chopper with a half bridge in combination with a split input voltage, wherein one output side connector is connected to the voltage centre point of the split input voltage via an inductor. In this case, however, the output voltage can never exceed the split input voltage, i.e., one half of the input voltage, and additional effort is necessary for generating the split input voltage.
For an inverter feeding electric energy into an AC power grid, a full bridge of actively controlled switches with parallel diodes, in which the centre points of the two half bridges are connected to the output side connectors via inductors, is known. The disadvantages of this known circuitry are the variable reference between the potentials at the input side and the output side connectors, and that the input DC voltage has to be at minimum as high as the grid peak voltage if no additional DC/DC converter is to be used.
When using a half bridge in combination with a split input voltage in an inverter for feeding electric energy into an AC power grid, the disadvantage occurs that the input DC voltage has to be at minimum as high as twice the grid peak voltage. Further, the effort for generating the split supply voltage is necessary.
There still is a need for a circuitry for a voltage converter that may be used as a DC/DC converter with protection against reversed polarity but also may be used in other DC/DC, DC/AC or AC/DC converters while avoiding the described disadvantages of prior art voltage converters.